The invention relates to an engine brake clutch device placed between an engine and a transmission and which is mounted particularly on a commercial vehicle to assure both the clutch function and the engine brake function.
The introduction of supercharged diesel engines poses two new problems in comparison with the atmospheric intake diesel engine.
The first problem relates to the clutch. The supercharged diesel engine, starting from its vacuum operation at idle, is able to provide its maximum torque only after a certain time and after having delivered a certain amount of energy, that must be dissipated in the clutch in the case of a uphill start of the vehicle. This greatly restricts the standard friction clutches in their service life.
The second problem relates to the braking of the vehicle. The supercharged diesel engine provides the same power as an atmospheric engine of much greater capacity. Consequently, the ratio of the engine torque to the braking torque is much higher for a supercharged diesel engine than for an atmospheric diesel engine. The supercharged engine holds the vehicle back much less than the atmospheric engine and the use of an engine brake becomes essential with a supercharged engine.
These two problems are poorly solved by prior art methods. Actually, with the atmospheric intake diesel engines whose engine torque was immediately available at low speed, the friction clutch made it possible to obtain good results with a satisfactory reliability. The atmospheric intake diesel engine equipped with an exhaust brake offered a satisfactory engine braking. However these prior art solutions no longer apply both to the supercharged engines and to the increase in the level of mechanization of the commercial vehicles.
In prior art systems as the clutch degrades, for a time, an amount of energy that it stores in its thermal inertia and evacuates slowly in the periods when, closed, it does not dissipate. A conventional clutch is designed for a sporadic and not extended use. If it is used continuously it is destroyed. The known engine brakes are provided to dissipate the energy for longer periods than a clutch and because of this possess a system for dissipation of the energy which in certain cases alters the efficiency of the vehicle.